There's a reason Harvey arrived at the battlefield so late.
His Five Consecutive Slash of Corpse Mountain and Blood Sea had too many flaws, allowing Silver Lamp to seize the opportunity to kick him away, sending him flying. Just as he was ready to regroup and charge back in, he was called by Igula who came flying by.
Igula only had one request—for Harvey to pretend to stop if Silver Lamp wanted to pause and explain, and Ash was willing to listen, then, taking the opportunity when she was unwary, kill her.
Harvey didn't ask why, nor did he say whether he agreed, and just returned to the battlefield. He saw Ash was still engaged in combat with Silver Lamp, so he drew his sword and joined the fray.
